An instantaneous voltage may happen on any electronic device and is generally caused by a circuit fault, a clap of thunder, or an electrostatic discharging. Components usually used for an overvoltage protection in a circuit involve a diode, a metal oxide varistor (MOV), a multilayer varistor (MLV), a transient voltage suppresser (TVS), and a surge protector.
An overvoltage of a circuit usually occurs with an overcurrent. Generally, a fuse is an element used for an overcurrent protection.
A capacitor is an energy-storage device. In an inductive circuit, in order to increase the power factor and the efficiency, a power capacitor is usually connected in parallel to the power system for compensating virtual work. The damage reason of the power capacitor is the insulation deterioration caused by an overvoltage.
In order that both the deterioration of the energy-storage device and the safety problem induced therefrom are avoided due to the overvoltage, it is necessary to seek architecture of a simple circuit for protecting the energy-storage device.